＜Review＞

Dynamics of NOx Secondary Substances in the Yoshino River basin area

NAEMURA Akihiko^*1,OKUDA Tomoaki^*2 and OKOCHI Hiroshi^*3

^*1Department of General Studies and Liberal Arts, Toita Women’s College, 2-21-17 Shiba, Minato-ku, Tokyo 105-0014, Japan
^*2Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Kanagawa 223-8522, Japan
^*3School of Creative Science and Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169-0072, Japan

Abstract

We analyzed O₃ concentrations in the middle reaches of the Yoshino River, class A river in Shikoku, and investigated river water quality data from the headwaters to the mouth of the river. The O₃ concentration in the atmosphere was 27.9 ppb, 0.85 times higher than that in Yonago, Tottori Prefecture, during the same period, and the highest value was assumed to be transboundary pollution from the Asian continent. The concentration of NO₃^-, which is linked to O₃ as a secondary substance, was not low at 18.4 uM in the headwaters. The headwaters were characterized by very low K⁺ concentrations due to the presence of mafic schist, Sanbagawa metamorphic belt. Thus, it is important to accumulate data on the watershed area in relation to the atmospheric and aquatic environments.

Key Words : Yoshino River basin, transboundary pollution, O₃, NO₃^-, Sanbagawa metamorphic belt

(Received June 23, 2022. Accepted December 14, 2022)